<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.js"></script>
</head>
<body>
    <p id="test">hello world</p>
    <script>
    var test =document.getElementById("test");
    test.onclick =function(){
        // alert(1);// 弹出框显示 1
        // innerHTML 改变元素内容
        this.innerHTML="change"
    }
    $("#test").click(function(){
        $(test).html("change")
    })
    </script>
</body>
</html>